1. Field of the Invention
The present invention relates to a method for reducing and/or decelerating the desorption of an antigen that has been adsorbed on an aluminum adjuvant as well as to the product thereof—namely the combination of a vaccine composition comprising the antigen adsorbed on the aluminum adjuvant and a container for the composition, said container having particular characteristics.
2. Summary of the Related Art
A large number of antigens are able to adsorb on an aluminum adjuvant, in particular at neutral pH or at a pH close to neutrality, which is the pH naturally required for compositions that have to be administered to mammals, including humans.
Provided that the amount of adjuvant is such that the antigen can actually adsorb on the adjuvant in an optimum amount when the two compounds are mixed together, the maximum degree of adsorption is very frequently achieved. However, over time, depending on the environmental conditions, the percentage of adsorbed antigen (adsorption rate) may decrease, and this desorption may constitute an instability factor.
Known environmental conditions that can affect the percentage of adsorbed antigen (adsorption rate) include, for example, variations in pH (even slight variations), and the addition of one or more medium component(s) or one or more additional antigen(s) that may compete with the first antigen for the adsorption sites on the adjuvant.
Conventionally, a ready-to-use multi-dose vaccine composition is loaded into vials, e.g., glass vials closed with a plastic stopper. Similarly, a single dose of a vaccine composition may be loaded in a mono-dose vial or a ready-for-injection syringe consisting, in a standard manner, of a reservoir containing the vaccine, a plunger that closes the reservoir at its distal end, and a device for administration, such as a needle attached at its proximal end. According to an alternative standard filling mode, the vaccine dose may also be loaded in a needleless syringe to which the practitioner adds a separately packaged needle at the time of the injection. The reservoir of the syringe is generally made of either glass or plastic and the plunger or the stopper is simply made of plastic, such as a chlorobutyl or bromobutyl polymer, without particular lamination. Standard glass or plastic syringes are sold, for example, by Becton-Dickinson; Gerresheimer A G, Schott A G, Germany; Nuova Ompi srl, Italy; and West Pharma/Daykio. In order to facilitate sliding, the plunger or stopper may have been immersed in a silicone-in-water emulsion so that a silicone film is formed at its surface. Standard plungers/stoppers are sold by Helvoet, Stelmi and West Pharma, for example; some of them already being sold coated with a silicone film (ref. B2 from West Pharma).
Whatever the container used for storage and the device used for closing the container, administration at the time of injection consists of using a syringe and sliding the plunger or the stopper/plunger combination so that the vaccine is delivered.